ES2770149B2 - Procedure and installation for the selective separation of gases in an oxy-combustion process by means of permeable oxygen membranes - Google Patents

Description

DESCRIPTION

Procedure and installation for the selective separation of gases in an oxy-combustion process by means of permeable oxygen membranes

field of invention

The present invention belongs to the field of gas separation membranes. Specifically, it refers to a new process for the simultaneous production of separate gaseous streams of at least two gases selected from nitrogen, oxygen, hydrogen and carbon dioxide from oxygen-permeable ceramic membranes in a process based on oxy-combustion. Therefore, its use is mainly oriented to oxy-combustion processes in which different oxidizer compositions can be used to achieve the desired product while, when oxidizing with pure oxygen, high flame temperatures are obtained and combustion is improved at the same time. that the contact of N2 with the products of the process is avoided.

State of the art prior to the invention

Introduction to oxygen permeation membranes

Mixed ion-electron conduction (MIEC) membranes are a type of dense ceramic membranes, in which oxygen ions diffuse from one side to the other through the properties of the crystalline structure due to a gradient of oxygen chemical potential between them. both sides of the membrane. The selectivity of these membranes is 100% to oxygen. These membranes operate at elevated temperatures (typically in the range of 700-1000°C) with high air pressures (1-2 MPa) fed to the retention side and vacuum on the permeation side, according to Air Products & Chemicals Inc., which has resulted in a breakthrough in the commercialization of MIEC membrane technology for pure oxygen productions.

The concept of separating pure oxygen from air using a MIEC membrane was explicitly proposed by Teraoka et al. in 1985. This research discovered oxygen permeation through perovskite-type oxides, i.e. La1-xSrxCo1-yFeyO3-5 (0<x<1, 0<y<1), in the temperature range of 450- 877 °C, and reached oxygen permeation flux of up to 3.1 ml cm ^-2 min ^-1 through a 1 mm thick SrCo0.8Fe0.2O3-5 membrane at 850 °C. Subsequently, perovskite-type oxides (ABO3) attracted considerable attention, strengthening the field of MIEC membranes. gradually. The development of new materials has been progressively improving, focused on improving the stability of membrane materials and their permeability. To improve stability, many kinds of membrane materials have been developed by improving cobalt-based perovskite materials by doping cations with stable valence state at the B-site and preparing cobalt-free perovskite materials and double-phase materials.

MIEC Applications

In addition to the separation of air for the production of pure oxygen, another important application of MIEC membranes is as membrane reactors in which catalytic reactions are integrated with the oxygen separation process. A typical catalytic reaction in MIEC membrane reactors is the partial oxidation of natural gas to produce synthesis gas. In this membrane reactor, air is fed to the holding side and natural gas is fed to the permeation side. Ni-based catalysts are usually applied on the permeation side that acts as a catalyst for the reaction. Oxygen permeated from the retention side reacts with natural gas to produce synthesis gas on the permeation side, and therefore this membrane reactor couples oxygen separation and catalytic reaction together with higher energy efficiency. The catalytic reaction consumes the permeated oxygen, thus increasing the oxygen chemical potential gradient across the membrane, and the oxygen flux is thereby increased considerably compared to the flux for pure oxygen production. Oxidative dehydrogenation of light alkanes to olefins and oxidation coupling of methane to ethane and ethylene were also considered in MIEC membrane reactors. The main advantage of catalytic membrane reactors is that the selectivity of these reactions can be improved compared to traditional fixed bed reactors, because lattice oxygen and not gaseous oxygen is the active oxygen species for catalytic reactions. oxidation. In the aforementioned MIEC membrane reactors, oxygen is selectively introduced into the reaction system; of course, oxygen can be selectively removed from the reaction system as long as an oxygen chemical potential difference exists across the membrane. The energy consumption of this type of MIEC membrane reactor processes can save by more than 60% compared to traditional industrial processes.

Principles of operation

Oxygen permeates through the membrane via three main steps: (1) oxygen exchange at the membrane interface on the air side, (2) diffusion through the membrane and (3) oxygen exchange at the membrane interface on the retention side. Surface exchange reactions are complicated because for every oxygen molecule that reacts there are 4 electrons reacting. The surface reaction can be simplified to O2+4 e-^ 2 O - considering electrons and oxygen ions as charge carriers and neglecting the diffusion path of oxygen ions. Considering electronic holes and oxygen vacancies as charge carriers, the surface exchange reactions are rewritten as: O2+2 V ^q ^2 OQ+4 h' where V ^q , OQ and h* denote oxygen vacancies, ions of oxygen occupying the corresponding oxygen site in the crystal lattice and the holes respectively. Although the global reaction seems simple, it collects many threads. For the holding-side oxygen exchange reaction, widely researched in the field of solid oxide fuel cells, steps such as adsorption, electron capture, dissociation, another electron capture, and incorporation into the crystal lattice occur. . The detailed mechanism is not yet clear, and may change depending on the material. The following is a widely accepted mechanism for the surface exchange of oxygen on the retention side. (i) Adsorption: O2(g )^ O 2(ad); (ii) reaction with one electron: O2(ad)+e-^O2(ad); (iii) change in adsorption state: O2(ad) ^O2(ad,bi); (iv) reaction with one electron: O2(ad,bi)+ 2 e-^ O 2-(ad,bi); (v) dissociation: O2-(ad,bi)^-2O2(ad); reaction with one electron: O2(ad)+e-^ O2(ad); (vi) incorporation of the crystal lattice: O -(ad)+VQ ^ O O. Each step could be the limiting step of the overall process. There are two types of diffusion pathways for oxygen ions across the membrane: through oxygen vacancies and through interstitial oxygen defects. For most perovskites and ABO3-type fluorites, oxygen ion transport follows the interstitial diffusion mechanism or a hybrid of both. In the oxygen permeation process, oxygen ion transport occurs from the retention side to the permeate side, while electrons are transferred in the reverse direction. Unlike an oxygen pump, based on pure oxygen ion conductors, MIEC membranes can transfer electrons internally, which simplifies the complexity of the system making it easy to apply on a large scale.

In summary, the transport of the oxygen ion is simultaneous to the transport of electrons or electronic holes (electronic carriers), so the material must have sufficient electronic conductivity under the operating conditions of the membrane. The driving force responsible for the transport of oxygen across the membrane is the difference in partial pressure of oxygen between the two sides of the membrane. In this way, the flow of oxygen through a membrane is determined by the temperature and the difference in partial pressure of oxygen as well as the thickness of the membrane.

Another crucial step in the oxygen separation process in ion transport membranes is gas exchange. As mentioned, the transport through the selective separation layer consists of the diffusion of oxygen ions and electronic carriers. Therefore, two surface reactions are necessary, a first one in which gaseous oxygen is adsorbed and transformed into oxygen ions on the surface of the membrane exposed to the feed gases, generally compressed air, and a second one, in which oxygen ions are converted to molecular oxygen and desorbed. For various reasons, these transport steps can be limiting and cause a decrease in permeation flux through the membrane. Among the different possible reasons, we can highlight: (1) the thickness of the selective separation layer is very small, so diffusion through the solid is much faster than gas exchange. Typically, this critical dimension is called "characteristic length" and is the quotient between the diffusion coefficient and the kinetic constant of the superficial gas exchange reaction under the operating conditions and composition of gases in contact with the membrane surface; ( 2) The surface of the membrane does not have appreciable catalytic activity for the oxygen activation reaction; (3) Gaseous atmospheres in contact with the surface or surfaces of the membrane discourage the adsorption/desorption of molecular oxygen and its evolution through the reaction O2 2e-^ O ^-2 In relevant processes from an industrial point of view, both the permeate and the feed usually present appreciable amounts of acid gases such as CO2 and SO2, which make this reaction difficult since they passivate or inactivate the surface and compete with the adsorption and reaction centers involved in the oxygen gas exchange reaction.This pernicious effect is accentuated as the operating temperature of the process decreases, especially below 850 °C, and when the concentration of SO2 and CO2 increases. Especially negative is the effect of SO2 gas, since concentrations above 5 ppm produce severe effects on oxygen permeation through the membrane.

The difference in oxygen partial pressure between both sides of the membrane can be achieved through two actions: (a) increasing the air pressure through compression stages; and/or (b) by lowering the partial pressure of oxygen in the permeate, which is possible by applying a vacuum, diluting the oxygen in the permeate by a stripping gas stream, or consuming the oxygen in the stripping chamber. This last option It usually consists of recirculating the exhaust gases from the furnace or combustion boiler, increasing the operating temperature at the same time. Likewise, in line with the second option, it is possible to pass a reducing gas (generally methane or other hydrocarbons) that consumes the oxygen that permeates through the membrane to give products of complete or partial combustion and release heat directly in contact with the membrane. ceramics.

Types of materials for MIECs membranes

To understand MIEC membranes, 5 classification criteria based on crystal structure, phase composition, chemical composition, geometry, and dense layer configuration are commonly used.

Considering their crystalline structure, MIEC membranes can be classified into perovskites, perovskite-derived membranes, and fluorites. Most MIEC membranes have a perovskite (ABO3) type crystal structure, where A is a large cation and B is a smaller cation. A perovskite is a crystal lattice built with octahedrons of BO ⁶ with A ions located in 12 localized interstices. Some MIEC have a crystalline structure similar to a perovskite, such as those from Ruddlesde-Popper (RP) with a formula of An+1BnO3n+1 (n=1,2, 3, ...). The crystal structure of this phase is similar to that of perovskite in that a number of perovskite blocks (n) have a shared corner with the AO-layer modified BO6 octahedron along the c-axis. Some MIEC have a fluorite structure, the typical example being CeO2 based materials.

If the membranes only have one type of crystalline phase, they are called monophasic membranes. Most perovskite membranes are single phase, eg La1-xSrxCo1-yFeyO3-5 (0<x<1;0<y<1). If the membrane has two phases and both contribute to oxygen permeation, it is called dual phase membranes. An example is the YSZ-Pd membranes, which contain a fluorite, YSZ, for the transport of oxygen ions and a metallic phase, Pd, for the transport of electrons. If the membrane has two or more phases and only one contributes to oxygen permeation, it is called a composite. The inert phase is added to improve some property of the material (mechanical resistance, for example). For example, in the composite SrCo ^0.8 Fe ^0.2 O ³ -s-SrSnO ³ it comprises two perovskites where the SrSnO3 phase is inert with respect to oxygen permeation, but improves the mechanical properties of the membrane.

At the beginning of the development of perovskite-type membranes, studies focused on those incorporating Co in the B crystalline position because Co-based membranes have high oxygen conductivity (for example, in Ba0.5Sr0.5Co0. 8Fe0.2O3-s). However, cobalt cations can be easily reduced to a lower valence state due to the weak Co-O bonding which is unstable in reducing environments. Therefore, Co-free perovskites have been developed. For example, BaCe0.05Fe0.95O3-s exhibit lower oxygen conductivities compared to the respective Co-based perovskite, but exhibit high stabilities even in H2 at elevated temperatures.

The most common geometries are flat, tubular and hollow fiber membranes. Finally, considering the configuration of the dense layer, we speak of self-supporting in membranes composed of a single membrane layer that is thick enough to support the integrity of the membrane and asymmetric when the dense membrane layers have a porous layer that allows thicknesses to be used. smaller since the integrity of the membrane is supported by the porous layer.

For practical use, high-temperature oxygen separation membranes via ion transport generally consist of the following components:

(i) A porous support, generally made either of the same material as the separating layer or of a material (ceramic or metallic) compatible with the separating layer. Compatible means that they have a similar expansion profile as a function of temperature and that a reaction between the two phases does not take place at high temperatures to give rise to third phases, which generally result in degradation and rupture of the membrane. The support porosity is usually between 20 and 60%, and its thickness is variable, typically below 2 mm.

(ii) A non-porous layer or film is placed on the porous support, preferably with a thickness of less than 150 pm. This layer is made up of oxides or mixtures of oxides and allows the simultaneous transport of oxygen ions and electronic carriers through it.

(iii) On the non-porous layer there is adhered a porous layer with a thickness preferably between 100 and 10 pm, made of a material that possesses mixed ionic and electronic conductivity as well as catalytic activity for oxygen adsorption/desorption and its dissociation and ionization. this layer catalytic allows to improve the processes of incorporation and elimination of gaseous oxygen.

In some cases, there is an additional porous catalytic layer between the porous support and the non-porous separation layer that has the function of improving the gas exchange stages, especially when the porous support has neither catalytic activity nor allows carrying out the transport of oxygen ions or electron carriers. Generally, the properties of the porous support and the additional porous catalyst layer are quite similar, although the specific surface area of the porous support is generally higher.

Optionally, another additional non-porous layer (v) may also be necessary. This layer would be located between the non-porous layer and the porous layer, and would serve to protect the separation layer against possible interactions or degradation reactions in contact with layer (iii) or with the operating gases in contact with the layer. porous. This additional layer must allow the transport of oxygen ions and oxygen carriers while being thermochemically compatible with the adjacent layers and with the gases with which it is in contact.

membrane reactor

A membrane reactor is a unit that combines a reagent system with a separation process using selective membranes in order to add or remove reagents or products in order to improve the efficiency of the system. In membrane reactors, membranes are introduced for the following purposes: selective reagent removal, catalyst retention, reagent dosing, catalyst support. All this leads to increases in the efficiency of reactions in systems limited by thermodynamic equilibrium, avoiding secondary reactions, protecting the catalyst from possible compounds that deactivate it, etc.

- Oxy-combustion

Oxy-combustion consists of using a stream of high purity O2 as oxidizer instead of air, as is done in conventional combustion processes, thus reaching higher flame temperatures with less fuel consumption and thus improving the combustion. The use of oxygen-rich oxidizers makes it possible to obtain combustion gases with a composition consisting mainly of CO2 and water vapour. The high concentration of CO2 in the exhaust gases in the oxy-combustion process facilitates its potential separation.

In fact, this oxy-combustion process in thermal or energy-intensive plants makes it possible to produce electrical energy or industrial products from fossil fuels while minimizing CO2 emissions, being technologically and economically feasible thanks to its integration with capture and CO2 storage. These processes have high energy efficiencies, which makes it possible to reduce fuel consumption and reduce the size of industrial units and equipment. Likewise, in the case of carrying out the combustion only with oxygen instead of air and not feeding N2 to the furnace, reactor or boiler, it is possible to considerably reduce NOX emissions (except for the nitrogen that the fuel current may contain). Therefore, this process has the advantage of facilitating the separation and capture of CO2, which can be subsequently liquefied, transported and stored or used in other industrial processes and minimizing CO2 and NOX emissions, as well as substantially increasing the energy efficiency of the process. Examples of energy-intensive industries that require the use of oxygen are the glass industry, incinerators, manufacturing of frits, enamels and paints, metallurgy, iron and steel, chemical, refining and petrochemical industries. One of the industrial sectors in which the use of oxygen makes oxy-combustion possible is glass melting and the manufacture of frits, glazes and ceramic colours. In this type of industry, the need to reach temperatures above 1500 °C inside the furnaces, in order to melt the mixture of raw materials that is introduced, is achieved by using oxygen instead of air in the gas burners. natural.

Oxygen membranes can also be applied in air enrichment, increasing the oxygen concentration from 21% to higher values, typically above 24%. This increase in concentration is necessary in certain combustion or chemical conversion processes in which the calorific value of the product to be treated, generally a fuel, is insufficient to maintain adequate operating conditions. A typical example of enrichment is the use in cement plants that use alternative fuels or incinerate residues during the manufacture of clinker.

Oxy-combustion aims to be one of the cheapest technologies for CO2 capture, its main drawback being the high demand for O2 that it presents and the cost that obtaining it entails. The great challenge of this technology is found in the production of O2 to be able to supply the high amounts that are required.

Industrial residues and streams disposed of in industrial plants

Most industrial plants generate currents that are not interesting for the process. Given the impossibility of finding a useful application for these currents, they generally end up being burned. In most cases, the greatest revaluation that is made with these currents is to take advantage of the heat of combustion to improve the energy efficiency of the process. In petrochemical plants and refineries, many currents are generated that end up being burned as they do not have any possible application (O2 and N2 production).

Oxygen is an important industrial gas that is widely used in chemical industries, ferrous metallurgy, glass, clean power generation, environmental protection, and so on. At present, cryogenic distillation is the only commercialized technology for the large-scale production of pure oxygen. Over the last 100 years, cryogenic technology has gradually matured, and there is only marginal room to reduce energy consumption in pure oxygen production. However, the current cost of pure oxygen production is still too high to be accepted by many industrial processes, such as the clean energy generation process, i.e. the CO2 capture flame cutting process, in which air is replaced by pure oxygen for the combustion of fossil fuels. Another matured technology for the separation of oxygen from air is pressure swing adsorption (PSA) using zeolites as adsorbents. However, the purity of oxygen produced through the PSA process is less than 95%, and it is economical only in medium or small scale oxygen separation. Therefore, PSA technology is not suitable for the aforementioned large-scale industrial processes. Compared with cryogenic distillation technology, MIEC membrane technology for pure oxygen production has low energy consumption and capital investment and is easily integrated with large-scale industrial processes.

Nitrogen is an industrial gas widely used as an inert gas as long as the oxygen that the gas may contain does not represent a risk of fire, explosion or possible oxidizing. In the same way as the production of oxygen, cryogenic distillation is the only way to produce it on a large scale and, for small or medium scale, PSA technology can also be competitive. The use of MIEC membrane modules to produce nitrogen is possible with sufficient membrane area through air-deficient oxy-combustion processes, so that the process air is significantly depleted of oxygen throughout the module, until it reaches very levels low of this one. So, in the same way as for pure oxygen production, compared to cryogenic distillation, MIEC membrane technology for pure nitrogen production has low energy consumption and capital investment and is easily integrated with large-scale industrial processes.

Turbomachines

Turbomachines are equipment that exchange energy between a rotor and a fluid. This energy transfer involves a change in fluid pressure, and it can go both ways: while turbines transfer energy from the fluid to the rotor, compressors transfer energy from the rotor to the fluid to cause changes in fluid pressure.

The main components of a turbomachine are: (i) a rotating element that carries vanes that operate in a fluid stream, (ii) a stationary element or elements that generally act as vanes or guides so that the direction of the flow and the conversion of power are adequately controlled, (iii) an input and/or output shaft, and (iv) the assembly. The rotating element that carries the vanes is also known by the names of rotor, runner, impeller, etc., depending on the particular application. The energy transfer occurs solely due to the momentum exchange between the flowing fluid and the rotating elements. Generally, all turbomachines are well insulated, with which the processes they house work in an adiabatic regime.

For incompressible fluids (most liquid fluids) pressurization of the fluid results in no (significant) change in internal energy and therefore no change in temperature due to the process.

For ideal gases, pressure changes in a turbomachine operating in an adiabatic regime cause the process to take place isentropically and the energy transferred between the rotor and the fluid generates changes in the internal energy of the fluid that translate into temperature changes. Considering the first law of temperature, the temperature changes in a turbomachine in adiabatic regime for an ideal gas are Y ^-1

They are described by the following equation: Tend=T0 (pend/p 0) And where Tend and T0 are the outlet and inlet temperatures respectively, pend and p0 are the outlet and inlet pressure respectively, and is the coefficient of adiabatic expansion. Therefore, considering the process, when the turbomachine causes an increase in the pressure of the gas, the temperature of the fluid increases and, when the turbomachine causes an expansion of the gas, the temperature decreases.

Finally, real turbomachines present losses due to the fact that the thermal insulation is not perfect and the friction of the fluid with the equipment. For this reason, in practice, turbomachinery performances are established on the ideal behavior for the complete characterization of the process. Generally, with respect to turbomachinery for incompressible fluids, the process is well defined with the mechanical performance. Regarding gas turbomachinery, the process is well defined with the mechanical performance and the isentropic performance.

This equipment is used in power plants to transform heat into electrical energy because the pressurization and depressurization energy increases with temperature. For this, a fluid is pressurized at low temperatures. The pressurized fluid is heated, generally from the heat of combustion. The heated fluid is introduced into a turbine where the mechanical energy transmitted to the rotor is transformed into electrical energy. Finally, the fluid is brought back to the starting conditions to close the cycle. The difference between the energy required by the system to pressurize the fluid and that obtained by depressurizing it in the turbine is transformed into electrical energy. This process is carried out mostly with water since it allows the pressurization to be carried out on a liquid (which is much less expensive than with a gas) and in this case it is called Rankine power cycle. There are also many applications that use a complete gas circuit and in this case it is called the Brayton power cycle, for example, aircraft turbines that incorporate within the same assembly, the air compressor, the combustion zone and the turbine. These types of assemblies (compressor, combustion zone, turbine) are called gas turbines.

Heat exchangers

Heat exchanger systems are systems that allow heat exchange between at least two fluids. They are equipment widely used in refrigeration or heating systems, power stations, chemical plants and petrochemical industry, among others. This equipment can be integrated into processes where it is required to incorporate (or evacuate) heat to the system. They are very versatile equipment, generally built using metal alloys to favor heat exchange.

Heat exchanger systems can arrange the flows of the different fluids in co-current, counter-current and cross-flow. In the co-current system, the hot and cold fluids go in the same direction. In the countercurrent system, the hot and cold fluid circulate through the equipment in opposite directions. In the cross flow system both flows go in perpendicular directions.

A conventional plate heat exchanger is made up of a succession of thin plates that are sealed by gaskets. The joints, in addition to avoiding the mixing of the fluids, establish the fluid circulation channels. The set of plates is compressed with two rigid metal plates making a distribution of parallel flows where one of the fluids circulates in the even channels, and the other fluid circulates in the odd channels. Today you can find gaskets made of graphite, rubber, and other materials, depending on the compatibility of the fluid to be used. The configuration of conventional plate heat exchangers is shown in Figure 15.

US6139604 describes a process for the production of oxygen and nitrogen from a feed gas containing a mixture of oxygen and nitrogen comprising compressing the feed gas in an air compressor to produce a compressed feed gas; contacting said compressed feed gas with a cathode side of an oxygen selective ion transport membrane, said feed gas being at a first temperature which is effective to promote the pressure driven transport of elemental oxygen from said side of the cathode on one side of the anode of said membrane oxygen-selective ion transport, after which a portion of nitrogen-rich gas remains on said cathode side; dividing said portion into a first oxygen-depleted portion at a first flow rate and a second oxygen-depleted portion at a second flow rate; recovering a high pressure nitrogen rich product gas from said first oxygen depleted portion; expanding said second oxygen-depleted portion in a turbine, thereby generating a combination of work and turbine exhaust of a nitrogen-rich product gas at low pressure, such that said turbine provides sufficient work for the compressor; and oxygen product gas is recovered from a permeate on said anode side of said oxygen selective ion transport membrane.

US2003039608 describes a method for producing hydrogen in which oxygen is stripped from an oxygen-containing stream to produce an oxygen permeate that is mixed with a hydrocarbon-containing stream and steam. Steam, one or more hydrocarbons, and permeated oxygen are reacted to produce a synthesis gas. Hydrogen is separated from synthesis gas by a transport membrane of hydrogen to produce a hydrogen permeate which, after cooling, is used to form a hydrogen product stream. The crude hydrogen-depleted synthesis gas is flared to heat the incoming oxygen-containing feed. US5102432 describes a process that uses a three or more stage membrane system, without the incorporation of a deoxo unit, to produce a very high purity nitrogen product in a manner. Nitrogen is produced from the air in three membrane stages, the compressed air passes into the membrane modules which at a feed air pressure between 50 to approximately 300 psig, at a temperature of approximately 90°F. Oxygen gas selectively permeates the membrane material used in such modules and is rejected at the relatively low pressure, the permeate side of the membrane. The nitrogen-rich non-permeate gas is recovered, essentially at the high pressure of the feed air. Second stage permeate gas, which has a lower oxygen concentration than air, can be recycled to the head of the plant for compression and recycling to the membrane system. Similarly, the third stage permeate gas, which has a lower oxygen content than the first stage, the non-permeate gas that is fed to the second stage, can be recycled to the second stage feed.

The present invention refers to a new process that allows industrial waste to be revalued to simultaneously and separately produce at least 2 gases selected from nitrogen, oxygen, hydrogen and carbon dioxide in at least two gas streams with high purity by combining different modules. oxygen permeable ceramic membranes. Therefore, the present invention provides a solution to improve the performance (permeate flow) of incomplete combustion and to revalue residual streams from a plant and transform them into products with greater added value.

The process allows the use of residual materials from different industrial processes. It is possible to treat small amounts of industrial waste (which over time represent a large residual load for a company and the environment) or large streams that are not optimally treated by adjusting the membrane area required in each membrane module.

Description of the invention

The present invention refers to a procedure that, using oxygen permeation ceramic flat membrane modules, allows the simultaneous production of at least two gases selected from substantially pure nitrogen, oxygen, hydrogen and carbon dioxide in at least 2 separate streams from a fuel stream and air, or from a fuel stream and a steam stream.

In this specification the expression "practically pure" means that its purity is at least 90% with respect to the total of an output stream, preferably 95% and more preferably 99.99%.

In this specification the expression "inlet stream of fuel in gas phase", "gasified stream of fuel", "inlet gas stream", are used interchangeably.

When referring to the membrane modules "first module"; "second module" and "third module" in embodiments in which at least three modules are used, the "first module" is the module in which operations are performed. corresponding to the first stages of the procedure, the second module is the intermediate module and the third module is the module in which operations corresponding to the last stages of the procedure are performed.

In the cases in which only two modules are used, reference is made to them maintaining the terminology used for the embodiments of the procedure that use three modules, that is, speaking of "first and third modules" when the second is dispensed with, or one speaks of "second and third modules" when the first is dispensed with,

The present invention refers to a process for generating and separating gases selectively characterized in that it comprises:

- a first stage in which an inlet stream of fuel in the gas phase is passed, comprising combustible substances whose oxidation gives rise to gaseous products, and an inlet stream rich in oxygen through at least two membrane modules of oxygen separation, so that the two streams come into contact through the membranes and a heat exchange takes place between them, - a second stage of selective diffusion of oxygen from the oxygen-rich stream, towards the fuel stream , and such that the output streams of the membrane modules are, on the one hand, an oxygen-depleted or completely oxygen-free stream and, on the other hand, a partially oxidized or fully oxidized stream,

- a third stage of recovery of at least two separate outlet streams, of at least two gases selected from among oxygen, nitrogen, carbon dioxide and hydrogen.

The gasified fuel stream contains combustible substances and its oxidation by reaction with oxygen produces gaseous compounds,

According to particular embodiments, the oxygen-rich inlet stream is selected from among air, water vapor, and combinations thereof.

According to additional particular embodiments, in the second stage the oxidation of the fuel is complete.

According to further particular embodiments, the oxygen-rich input stream is air and the two separate output streams are nitrogen and carbon dioxide.

According to further particular embodiments, the oxygen-rich input stream is air and there are at least three separate output streams: oxygen, nitrogen, and carbon dioxide.

According to further particular embodiments, the oxygen-rich input stream is steam and the two separate output streams are hydrogen and carbon dioxide.

According to additional particular embodiments, the oxygen-rich stream is water vapor and there are at least three separate outlet streams: they are oxygen, hydrogen, and carbon dioxide.

Ceramic oxygen permeation membranes need high temperatures to achieve efficient oxygen transport (>600, or even >650°C), so the inlet streams to the modules (one rich in oxygen and the other with low contents or partial pressures of oxygen) must be pre-conditioned to enter the modules at temperatures higher than 600°C. For this, the inlet streams can be pre-heated by means of heat exchange devices using the hot outlet streams in order to improve energy efficiency.

In the process of the invention, the exchange of gases between the two input currents to the membrane modules is carried out at a temperature between 600 °C and 1500 °C. Preferably, the exchange of gases between the two input streams to the membrane modules is carried out in such a way that the temperature of the gases does not exceed 1500 °C.

Oxygen diffuses preferentially at temperatures between 600-750°C.

Inlet streams enter the membrane modules at a higher temperature of 600°C or higher.

The average operating temperature of the membrane modules is, according to particular embodiments, between 750 and 1250 °C.

In order to improve the transport of oxygen through the membranes, the procedure can also include a pressurization stage in a first gas compressor device, of the inlet streams at absolute pressures between 2 and 15 bar, obtaining pressurized inlet streams. .

The pressurization of the combustible gas current by the first gas compressor must be sufficient to overcome the pressure losses due to the gas conduction lines, the heat exchanger systems and the membrane modules.

The pressurized inlet streams can be subjected to a preheating stage with heat given off by the outlet streams, obtaining preheated pressurized inlet streams.

The flows of the combustible gas stream and the oxygen-rich stream can be arranged in countercurrent.

The oxygen-depleted outlet stream can be fed into a turbine for energy recovery. To optimize the pressurization (and depressurization) of the oxygen-rich line, the turbine can be connected to the same axis as the first gas compressor device.

According to particular embodiments illustrated in example 1, the procedure is carried out in at least three modules selected from among:

- a first membrane module in which the gasified fuel stream is partially oxidized,

- a second membrane module in which the gasified fuel stream is completely oxidized,

- a third membrane module in which oxygen extraction is carried out.

In these embodiments, cross-flow, co-current flow, or counter-current flow can be used in the second membrane module.

With countercurrent flows, heat exchange is better and better temperature control can be achieved and very hot spots can be avoided at certain points of the membrane modules, which can cause risks of mechanical failure of the module.

In these embodiments, CO2 and liquid water are produced from the oxidized combustible gas stream that exits the second module, the water being condensed by means of a condenser-separator arranged at the outlet of the second module, from which two output streams exit: a combustible gas stream oxidized -composed mainly of CO2- and a current of liquid water.

According to additional particular embodiments, carbon dioxide and nitrogen are obtained, and a recirculation of part of the carbon dioxide or nitrogen obtained in the process is carried out, so that a dilution of the combustible gas stream is produced and the gases are absorbed. oxidation heats

According to additional particular embodiments, illustrated by example 2, three membrane modules are used, and such that

- all the oxygen-rich inlet stream coming from the second heat exchanger is fed into the second membrane module,

- the oxygen-depleted stream exiting the second membrane module is metered by means of a valve system that partially circulates this stream:

- to the first membrane module as a stream supplying oxygen as an oxygen-depleted stream containing an amount of oxygen less than the stoichiometric amount to fully oxidize the gasified fuel stream, and - to the third membrane module as a stream supplying oxygen to the third module and the turbine.

According to additional particular embodiments, illustrated by example 3, the second and third membrane modules are used,

- all the gasified, fuel, pressurized heated input stream coming from the first heat exchanger is introduced into the second membrane module, and

- all the oxygen-rich inlet stream coming from the second heat exchanger is fed into the second membrane module,

According to additional particular embodiments, illustrated by example 4, only the first and second membrane modules are used,

- the oxygen-depleted outlet stream from the second membrane module is recirculated to the turbine as turbine inlet stream.

A CO2 outlet stream and an oxygen-depleted stream are obtained from the modules where partial oxidation occurs and both outlet streams are pressurized after being cooled.

According to additional particular embodiments, illustrated by example 5, the first and third membrane modules are used,

- the partially oxidized fuel gas stream leaving the first membrane module and the oxygen-depleted output stream from the third membrane module are introduced into a combustor to finish oxidizing the partially oxidized fuel material of the gas stream, and

- the output current of the combustor is introduced into the turbine.

According to additional particular embodiments, illustrated by example 6, additional membrane modules are used, in addition to the first, second and third membrane modules, in the additional modules the streams of gases produced in the first and second membrane modules are purified. membrane module removing oxygen from them, and

- the combustible gas stream enters the additional modules as an entrainment stream.

In this case, the membrane modules can have a countercurrent flow distribution to ensure complete oxygen exchange from the streams to be purified to the fuel streams.

The off-gas streams can be purified by oxygen-permeating polymeric membranes, after being cooled to room temperature and pressurized.

In the process of the invention, the source of the combustible gasified current can be biomass, which is gasified by means of a thermochemical reactor, the input currents to the thermochemical reactor being:

- biomass

- a drag stream made up of an inert gas and, optionally, steam,

- and, optionally, an inlet stream rich in oxygen.

A particular embodiment of the process in which the gas phase input stream comprises biomass is shown in example 7.

The process of the invention makes it possible to obtain two or more output gas streams with a purity greater than 95%, on a dry basis, of one of the following gases chosen from N2, O2, H2 and CO2.

The process of the invention makes it possible to obtain, according to particular embodiments, as different output currents, at least N2 and CO2 with purities greater than 95%.

The process of the invention makes it possible to obtain, according to particular embodiments, as different output currents, at least N2 and O2 with purities greater than 95%.

The process of the invention makes it possible to obtain, according to particular embodiments, as different output currents, at least N2, CO2 and O2 with purities greater than 95%.

The process of the invention makes it possible to obtain, according to particular embodiments, at least one pressurized stream with an absolute pressure greater than 4 bar, with an output made up of N2, CO2 or O2 with purities greater than 95%.

The input stream, which contains combustible materials, can comprise one or more products selected from among CO, H2, H2S, methane, liquefied petroleum gas (LPG), alcohols, olefins, peroxides, aromatic compounds, organic acids, organic amines, naphthas , asphalt, bitumen, gas oil, vegetable, animal or mineral oils or fats, coals, and mixtures thereof.

The composition of the fuel, as well as its reaction mechanism, must be considered for the design of the first and second membrane modules that receive the input currents in order to optimize heat transfer and avoid areas within each module with excessive temperatures. . Figure 12 shows the adiabatic flame temperature for different materials.

According to particular embodiments of the process, hydrogen is obtained. To obtain hydrogen, the stream rich in oxygen (C2) is a stream of water vapor or a stream of air mixed with water vapor. In this case, the oxygen-rich stream is pumped with a hydraulic pump. Subsequently, an evaporator is required to gasify the oxygen-rich stream and a heat exchanger to raise its temperature to the inlet temperature of the first module (which we can call the operating point). In this case, the oxygen exchanged through the membrane modules comes from the oxygen of the water molecule, producing hydrogen in the part of the module that contains the gas (or steam chamber) If the fuel stream comprises hydrocarbons, the overall process is based on the respective steam reforming reactions of said hydrocarbons. These reactions are highly endothermic and, consequently, a decrease in temperature would occur as this process progresses, which, in turn, would deactivate the phenomena of oxygen transport through the membrane. In this way, using this process for the production of hydrogen requires heat sources in the membrane modules to prevent the decrease in temperature from limiting the process. If the fuel stream is CO based, the overall reaction is water gas shift. This reaction is exothermic, so this energy must be taken into account to ensure that the temperature inside the equipment does not skyrocket.

In the process of the invention, the oxygen ion exchange membranes have been integrated into an oxidation process of a fuel stream and a gas stream with oxygen (typically air) to simultaneously obtain N2, O2, H2 and CO2. This process takes advantage of the heat generated in the oxidation process to heat the different input currents and maintain the temperature of the different units that make up the system. Obtaining practically pure nitrogen is produced from an assembly where the fuel and air currents are in countercurrent and the air that is introduced to this assembly is less than the stoichiometric quantity to oxidize all the oxidizable material in the fuel current. CO2 production occurs from an assembly where the amount of oxygen exchanged is greater than the stoichiometric amount of the input fuel and after a separation of the water that may have formed in the different oxidation reactions. The production of oxygen occurs using the air used after having produced the CO2 and N2 in an assembly where the oxygen is extracted through a vacuum system. The different oxygen ion exchange membrane assemblies must act as oxygen and heat exchangers and must be properly designed for the process to be efficient. The final used air can be revalued in a turbine.

The procedure of the invention presents several advantages with respect to the state of the art, such as the fact that it achieves three actions to take place simultaneously: - the heat exchange that takes place in the membrane modules

- the transfer of matter that is produced and

- the reaction of oxygen with fuel.

The present invention also relates to an installation for carrying out the defined process.

When referring to the installation, the expressions "current line"; or the terms "duct" or "current" are used interchangeably.

The installation to carry out the defined procedure comprises at least:

- two oxygen separation membrane modules

- gas compressors that drive the input currents to the membrane modules

- heat exchanger devices between incoming or outgoing gas streams in membrane modules,

- a turbine arranged to receive at least gas from one of the membrane modules and produce work

- at least two separate individual flue gas stream lines from the oxygen separation membrane modules

and wherein each oxygen separation membrane module comprises an array of planar parallel membranes.

These characteristics mentioned in the previous paragraph are common in the installation for all implementations.

Compressors allow the compression of process gases at absolute pressures in the range between 0.5 and 15 bar.

The purpose of the turbine or set of turbines is to produce electrical and/or mechanical energy from the decompression of streams made up of hot gases from other process units.

The installation can additionally include at least one membrane module based on ceramic ionic and electronic conductors, and made up of parallel and flat channels that facilitate contact between gaseous currents isolated by the membrane and that has as the only input, a current rich in oxygen, and as outputs (i) a rejection current, depleted in oxygen with respect to the input current, and (ii) a current rich in oxygen with a purity greater than 95% and which is located at vacuum -between 1 and 750 mbar-

The membrane modules of the facility may comprise separation membranes based on ceramic ionic and electronic conductors, and porous ceramic supports.

Furthermore, the membrane modules may comprise a catalyst for the effective oxidation of the fuel components with oxygen diffusing through the membrane.

The flow of the two currents, which facilitates the exchange of matter and heat, in the membrane modules can be carried out in countercurrent and sufficient length is provided for an effective exchange.

The facility may additionally include at least one separation module based on porous polymeric or inorganic membranes selective for nitrogen diffusion and which allows a nitrogen-enriched stream to be obtained at temperatures below 400°C from a pressurized air supply. .

The installation may additionally comprise a water and gas separation unit.

In the installation of the invention, at least one compressor and one turbine can be axially coupled to use the mechanical energy of the expansion in the compression of a gas stream. The coupling can be carried out by means of axial turbine-compressors or turbocharger-type systems.

According to particular embodiments illustrated in figure 1, the installation comprises at least:

- a first oxygen separation membrane module, which has two inlets for - a first gasified stream of fuel and

- an inlet stream rich in oxygen.

- a first gas compressor that makes it possible to pressurize the combustible gas stream, and which leaves the compressor as a pressurized combustible gas stream, towards - a first heat exchanger device that allows the pressurized combustible gas stream to be heated and which leaves the exchanger as a stream preheated pressurized fuel gas

- a second gas compressor that makes it possible to pressurize the oxygen-rich inlet stream, and which leaves the compressor as a pressurized oxygen-rich inlet stream

- a countercurrent gas heat exchanger device that allows heating:

- the oxygen-rich inlet stream pressurized to the inlet temperature to the first membrane module, and exiting the heat exchanger as a heated pressurized oxygen-rich inlet stream,

- and an oxygen-depleted stream coming from a turbine

- at least two separate individual gas outlet stream lines from second and third oxygen separation membrane modules

and wherein each oxygen separation membrane module comprises an array of planar parallel membranes.

According to additional particular embodiments illustrated in figure 2, the installation comprises three membrane modules and in which the outlet stream from the second membrane module is separated into three stream lines, each of which comprises a dosing valve, and of which two of the current lines lead to the first or to the turbine allowing the recirculation of gases, and the third current line leads to the third membrane module, allowing the progress of the process.

According to additional particular embodiments illustrated in figures 3, 4, 5, the installation comprises two membrane modules.

According to additional particular embodiments illustrated in figures 6 and 7, the installation comprises more than three membrane modules.

Throughout the description and claims, the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and characteristics of the invention will emerge in part of the description and in part of the practice of the invention The following examples are provided by way of illustration, and are not intended to be limiting, of the present invention.

Figure 1. Diagram of the revaluation process of industrial currents from oxygen permeation ceramic membrane modules for the simultaneous production of CO2, N2 and O2.

Figure 2. Diagram of the revaluation process of industrial currents from oxygen permeation ceramic membrane modules for the simultaneous production of CO2, N2 and O2 alternative configuration of the C2 current.

Figure 3. Diagram of the revaluation process of industrial currents from oxygen permeation ceramic membrane modules for the simultaneous production of CO2 and O2.

Figure 4. Diagram of the revaluation process of industrial currents from oxygen permeation ceramic membrane modules for the simultaneous production of CO2 and N2.

Figure 5. Diagram of the revaluation process of industrial currents from oxygen permeation ceramic membrane modules for the simultaneous production of N2 and O2.

Figure 6. Diagram of the revaluation process of industrial currents from permeation ceramic membrane modules, purifying the N2 and CO2 currents through ceramic membrane modules.

Figure 7. Diagram of the process of industrial flows from ceramic oxygen permeation membrane modules integrated into a biomass gasification (or pyrolysis) process.

Figure 8. Plans of the oxygen permeation membrane module with the gas currents distributed in cross flow. Module with 20 membranes. a: general view of the module; b: plan view of the module; c: plan view of section BB; d: plan view of section CC; e: zoom of the section plane BB; f: zoom of the section plane CC.

Reference (70) shows the spacers between membranes and reference (72) shows the outer cover of the module.

Figure 9. Plans of the oxygen permeation membrane module with the gas currents distributed in co-current or counter-current. Module with 20 membranes. A: general view of the module; b: plan view of the module; c: view of the section plane AA for a distribution of flows in co-current; d: view of the section plane BB for a distribution of flows in co-current; e: zoom of the section plane AA; f: zoom of the section plane BB; g: view of the section plane AA for a distribution of flows in countercurrent; h: view of the section plane BB for a distribution of countercurrent flows.

Figure 10. Plans of the oxygen permeation membrane module with three passes with 6 membranes per pass. A: general view of the module; b: plan view of the module; c: view of the section plane BB for a distribution of flows in co-current; d: view of the section plane CC for a co-current distribution of flows; e: zoom of the section plane AA; f: zoom of the section plane BB; g: view of the section plane BB for a countercurrent flow distribution; h: view of the section plane CC for a countercurrent flow distribution.

Figure 11 shows the results of example 1 where a practical case of the first membrane module (6) has been studied with a mixture of CO-CO2 as a fuel gas stream and air as a stream rich in oxygen. Profiles of temperature (T) and mole fraction of oxygen (xO ² ) along the air chamber (L: longitudinal coordinate of the membrane module) for the oxygen permeation membrane module with oxygen deficit in the flow stream. air (7) for different dilutions of stream (7) with CO2 (r = — ^CO2

C1-). Results for a membrane module of a total membrane area of 380 cm ² and a CO and CO 2 feed (57.1% CO) for stream (5) with inlet streams at 700°C. a: explanation of the process; b: configuration of co-current flows; c: configuration of countercurrent flows; d: results for an air intake at 25% of the stoichiometric amount; e: results for an air intake at 50% of the stoichiometric amount; f: results for an air intake at 75% of the stoichiometric quantity.

Figure 11.a shows a view of the first membrane module. Figures 11.b and 11.c show a simplified view of the passage of gas streams through the fuel (69) and air (71) chambers for a co-current flow distribution (solid lines in Figures 11. c, 11.d and 11.e) and countercurrent (dashed lines in Figures 11.c, 11.d and 11.e) respectively.

Figure 12. Adiabatic flame temperature (T) for various fuels with air. They are important for understanding the mechanism of the procedure and the results. F1: hydrogen, F2: methane, F3: natural gas, F4: acetylene, F5: ethane, F6: butane, F7: gasoline, F8: benzene, F9: kerosene, F10: light diesel, F11: medium diesel, F12: diesel heavy, F13: naphthalene, F14: pentadecaene, F15: eicosane, F16: bituminous coal, F17: anthracite. (https://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html).

Light diesel is defined as a by-product obtained from the atmospheric distillation of petroleum that starts boiling between 175 and 200°C and ends between 320 and 350°C.

Medium diesel: intermediate is defined as a by-product obtained from the distillation of petroleum, whose boiling takes place in an interval between the boiling of light diesel and the boiling of heavy diesel.

Heavy diesel is defined as the residual product of petroleum distillation whose boiling range is between 423 and 600°C.

Figure 13. Temperatures (T) for the oxygen permeation membrane module fed with different amounts of air (excess air to cause complete oxidation of the fuel). A represents the ratio between the introduced air (11) and the stoichiometric air to oxidize all the combustible material in the combustible gas stream (8). Results for a membrane module with a total membrane area of 380 cm2 and a CO and CO2 feed (9.5% CO) for (11) with the inlet streams at 700°C. a: explanation of the process; b: air outlet temperatures for co-current flows (14); c: air outlet temperatures for countercurrent flows (14); d: maximum temperatures inside the module for co-current flows (10); e: maximum temperatures inside the module for countercurrent flows (10). Points within the graphs indicate cases where complete oxidation of the input fuel is achieved.

Figure 14. Oxygen extracted as a function of the process conditions and the membrane area (A) used for the third membrane module. The oxygen extraction (E02) has been calculated by means of the relation between the extracted oxygen and the oxygen that enters the membrane module. Air inlet of 22.4m3CN/h (CN: normal conditions). a: process scheme; vacuum pressure of 50mbar (b, c and d); vacuum pressure of 100 mbar (e, f and g); air at atmospheric pressure (b and e); air at 2.5 bar (c and f); air at 5 bar (d and g).

Figure 15. Conventional configuration of a flat plate heat exchanger.

examples

Figures 1 to 7 show examples of various embodiments for the method and installation of the invention.

In all the embodiments of the installation of the invention, the same references are used for the elements common to all of them, which are detailed below: The installation has two main conduits or input stream lines: a stream of input material - combustible gas stream -(C1) and a stream rich in oxygen (C2).

The installation has several conduits or output current lines: the oxygen-depleted current (C3) and each of the gaseous currents that are obtained according to the application of the process.

The combustible gas stream (C1) is driven by a first gas compressor (2).

The input stream to the first compressor (2) is the input combustible gas stream (1). The output stream of the first compressor (2) is the pressurized fuel gas phase stream (3).

The pressurized combustible gas stream (3) is heated up to the inlet temperature to the membrane modules by means of a first heat exchanger device (4).

The input stream to the first heat exchanger (4) is the combustible gas stream (3) that comes from the first compressor (2).

The output stream of the first heat exchanger system (4) is the preheated pressurized combustible gas stream (5).

The oxygen-rich stream (C2) (27) is driven by a second gas compressor (28).

The input stream to the second compressor (28) is the oxygen-rich input stream (27).

The output stream of the second compressor (28) is the pressurized oxygen-rich input stream (30).

The oxygen-rich stream (30) is heated to inlet temperature to the membrane modules by a gas heat exchanger (31).

The input streams to the heat exchanger device (31) are the oxygen-rich stream (30) coming from the compressor (28) and an oxygen-depleted stream (32) coming from the turbine (33). One of the output streams of the heat exchanger system (31) is the oxygen-depleted stream (C3), which reaches the outlet through the stream line (35). One of the output streams of the heat exchanger system (31) is the oxygen-rich stream (34)

To optimize the pressurization (and depressurization) of the oxygen-rich line, the compressor (28) and the turbine (33) can be connected to the same shaft (29).

Example 1

Figure 1 shows a diagram of a particular example of the procedure and the installation to carry it out.

In this particular case, the installation has three main modules of oxygen permeation ceramic membranes (M1, M2 and M3), also designated as (6), (10) and (15). These modules have flat parallel membranes whose total area is divided into different sections within each module. The arrangement of the currents, geometry of the module, path of the currents of each module are focused on optimizing the process that it houses and optimizing the heat transmission between the different currents that pass through it.

The input material stream (C1) (gasified stream, or gas phase stream, of fuel) contains combustible substances and whose complete oxidation by reaction with oxygen produces gaseous compounds. The oxygen-rich inlet stream (C2) is composed primarily of O2 and N2.

The combustible gas stream (3) is heated up to the inlet temperature to the first membrane module (6) by means of the first heat exchanger device (4). The input stream to the heat exchanger (4) is the combustible gas stream (3) coming from the compressor (2). The output stream from the heat exchanger (4) is the heated pressurized combustible gas stream (5).

The oxygen-rich stream (C2) (30) is heated to inlet temperature by a second heat exchanger (31). The input streams to the heat exchanger (31) are the oxygen-rich stream (30) coming from the compressor (28) and the oxygen-depleted stream (32) coming from the turbine (33). In this case there are two outlet streams from the second heat exchanger system (31), which are an oxygen rich stream (34) and the oxygen depleted outlet stream (35).

The dosing or control of the volumetric flow of the incoming and outgoing gas currents to the oxygen permeation membrane modules (6) and (10) is carried out by means of a system of valves (38 and 39). This dosing must be carried out considering that the first membrane module (6) is introduced with an amount of air that contains amounts of oxygen less than the stoichiometric amount to completely oxidize the fuel gas, while the second membrane module (10) is introduced with a amount of air that contains an excess of oxygen with respect to the stoichiometric amount. Consequently, the heated oxygen-rich stream (34) is split into two streams (36 and 37). The input stream to the dosing valve (38) of the first membrane module (6) is a stream rich in oxygen (36). The outlet stream from the dosing valve (38) of the first membrane module is a stream rich in oxygen (7). The inlet stream (39) to the dosing valve of the second membrane module (10) is an oxygen-rich stream (37). The outlet stream from the dosing valve (39) of the second membrane module (10) is a stream rich in oxygen (11).

The purpose of the first membrane module (6) is to produce - according to this particular embodiment - nitrogen from the combustible gas stream and a stream rich in oxygen. The input currents to the membrane module (6) are the combustible gas current (5), which comes from the exchanger (4) and the oxygen-rich current (7) which comes from the dosing valve (38). The outlet streams from the membrane module (6) are the partially oxidized fuel gas stream (8) and the oxygen-depleted stream (9) whose composition is practically pure N2. In this embodiment of the process, the oxygen-rich stream (7) is introduced in an amount less than the minimum amount to oxidize all the combustible material carried by the combustible gas stream (5). Bearing in mind that a less than stoichiometric amount of oxygen has been introduced into the combustible gas stream (5), the combustible gas stream chamber will maintain a very low oxygen pressure (of the order of mbar) and, therefore, the The driving force of the oxygen transport process will be very high. In this module (6), it must be ensured that the output oxygen-depleted stream (9) is practically pure nitrogen and that the heat transfer between the streams that pass through the module is efficient. For this, the input flows to the module M1 (6) (the combustible gas current (5) and the air current (7)) are arranged in countercurrent. The oxygen that is exchanged through the membrane reacts with the combustible material by raising the temperature, thereby improving the oxygen transport properties of the material. If necessary and in order to avoid excessive heating due to the oxidation of combustible gases, part of the carbon dioxide or nitrogen obtained in the process can be optionally recirculated and thus dilute the combustible gas stream (5). and absorb the heats of oxidation. Whereas the combustible material in the combustible gas stream (5) presents a composition of CxHyOz, the maximum nitrogen production that could be achieved is 2x+y/2-z • 079 mol of N2 for each mol of combustible material.

The purpose of the second membrane module (10) is to completely oxidize the combustible gas stream (8) that comes out partially oxidized from the first membrane module (6). For this, an excess (in flow rate) of the oxygen-rich stream is introduced into the process with respect to the minimum quantity to oxidize all the combustible material carried by the combustible gas stream (8). The input streams to the second membrane module (10) are the combustible gas stream (8), which comes from the outlet of the first membrane module (6), and the oxygen-rich stream (11). The outlet streams from the second membrane module (10) are the combustible gas stream (13), which is composed mainly of CO2 and water vapor (unless the combustible material of the gasified stream is CO, in which case the gas stream output fuel will be composed mainly of CO2), and the oxygen stream (14), depleted in oxygen with respect to C2. The oxygen that is exchanged through the membrane reacts with the combustible material by raising the temperature, thereby improving the oxygen transport properties of the material. The amount of air that is introduced into the second module (10) M2 must be high enough to ensure that the oxygen exchanged causes the complete combustion of all the combustible material that the combustible gas current has (contained in hydrocarbons and in carbon monoxide either negligible) and to avoid excessive heating of the module due to combustion processes, through an effect of dilution and distribution of heat in a large volumetric flow. Finally, for this module (10) the gases can be distributed in crossed flows, in cocurrent flows or in countercurrent flows. The final choice of the module is subject to the needs: for example, considering that the oxidation processes can generate excessive temperatures inside the module, a co-current distribution could be necessary that allows a more gradual dosing of the oxygen exchanged by the module membranes and In this way, reduce and control the progress of oxidation reactions to avoid excessive increases in temperature.

The third membrane module (15) has as its objective the extraction of oxygen from a stream rich in oxygen. The input current to the membrane module (15) is the oxygen-depleted current (14) with respect to the current (C2) coming from the second membrane module (10). The output currents of the third membrane module (15) they are the oxygen-depleted stream (16) and the extracted oxygen (13). Oxygen is extracted by imposing a vacuum on the entrainment chamber and thus achieving a high driving force. As no additional phenomenon occurs, this module works in an isothermal manner as long as it remains well insulated thermally.

The completely oxidized combustible gas stream (13) coming from the second membrane module (10) is mainly composed of carbon dioxide and water vapor. For its separation, the water vapor is condensed, cooling the stream to room temperature (15 - 25°C). For this, use is made of a heat exchanger device (22). The input stream to the heat exchanger system (22) is the fully oxidized combustible gas stream (13) coming from the second membrane module (10). The output stream to the heat exchanger system (22) is the fully oxidized fuel gas stream (23).

Optionally, a condenser-separator (24) is used to evacuate the condensed liquid water from the completely oxidized fuel gas stream (23) coming from the third module (15) and which has passed through the heat exchanger (22). The input stream to the condenser-separator (24) is the completely oxidized combustible gas stream (23) coming from the heat exchanger device (22). The outlet streams from the condenser-separator (24) are the completely oxidized combustible gas stream (25), composed mainly of CO2, and a stream of liquid water (26).

Alternatively, in the event that the starting combustible gas stream (C1) is a mixture of CO and CO2, the completely oxidized combustible gas stream coming from the second membrane module (13) will be composed mainly of CO2, so that it needs the separator condenser (24) and the output current of the heat exchanger device (23) would be the final CO2 current.

The oxygen stream that is extracted from the third module (17) must be cooled before being introduced into a vacuum generation system (20). For this, a heat exchanger device (18) is required that lowers the temperature of the oxygen stream to approximately room temperature. The input stream to the heat exchanger device (18) is the oxygen stream (17) that comes from the outlet of the third membrane module (15). The output stream of the heat exchanger device (18) is an oxygen stream (19). Finally, the vacuum generation unit (20) drives the oxygen and pressurizes it, inducing a depression or vacuum upstream. The input stream for the vacuum generation system (20) is the oxygen stream (19) coming from the heat exchanger device (18). The output stream for the vacuum unit (20) is the oxygen stream at the required operating pressure (21).

Finally, the stream depleted in oxygen (16) is introduced into a turbine (33) for its energetic revaluation. The inlet stream to the turbine (33) is a stream depleted in oxygen (16). The output stream from the turbine (33) is the oxygen-depleted stream (32) coming from the third membrane module (15). To optimize the pressurization (and depressurization) of the oxygen-rich line, the compressor (28) and the turbine (33) can be connected to the same shaft (29).

Figure 11 shows the results of this embodiment relative to the first membrane module (6) with a mixture of CO-CO2 as combustible gas stream (5) and air as oxygen-rich stream (7). Figure 11.a shows a view of the first membrane module. Figures 11.b and 11.c show a simplified view of the passage of gas streams through fuel (69) and air (71) chambers for a co-current flow distribution (solid lines in Figures 11. d, 11.e and 11.f) and countercurrent (dashed lines in Figures 11.d, 11.e and 11.f) respectively. Figure 11.d shows the results of the air chamber (71) temperature profiles and the oxygen mole fraction in the air chamber (71) along the longitudinal coordinate of the membrane module considering an input of air (7) corresponding to 25% of the minimum amount to be able to oxidize all the combustible material of the inlet fuel gas stream (5). Figure 11.e shows the results of the profiles of temperatures in the air chamber (71) and the mole fraction of oxygen in the air chamber (71) along the longitudinal coordinate of the membrane module considering an input of air (7) corresponding to 50% of the minimum amount to oxidize all the combustible material in the inlet fuel gas stream (5). Figure 11.f shows the results of the temperature profiles in the air chamber (71) and the mole fraction of oxygen in the air chamber (71) along the longitudinal coordinate of the membrane module considering an input of air (7) corresponding to 75% of the minimum amount to be able to oxidize all the combustible material of the inlet fuel gas stream (5). The results show that, for the cases considered by example 1, considering a fixed total membrane area, for the first membrane module (6) the arrangement of countercurrent flows makes it possible to generate nitrogen currents whose oxygen content is less than 1%, while in the case of co-current, excessively diluting the fuel current (5) causes the module to not heat efficiently and, therefore, oxygen does not permeate because the resistance of the membrane acts as limiting. It is observed that in the co-current case, as the oxidation reactions take place, the heat is used to heat both the CO-CO ² current and the air current. On the other hand, oxygen is consumed in the same direction. So, for the co-current case, the temperature increases as the driving force decreases and, due to this, the oxygen transport phenomena through the membrane are activated as the driving force decreases. On the other hand, the countercurrent case, the direction of the fuel causes the heating of the module to occur in the opposite direction in which the driving force decreases. This means that the hottest areas and the areas with the greatest driving force are located in the same area of the module. Thus, for countercurrent distribution, the phenomena of oxygen transport through the membrane are activated as the driving force increases.

Figure 13 shows the results of example 1 where a practical case of the second membrane module (10) has been studied with a mixture of CO-CO ² as a combustible gas stream (8) and air as a stream rich in oxygen (11). A practical case has been studied for the arrangement of flows in co-current (Figures 13.b and 13.d) and countercurrent (Figures 13.c and 13.e) in the second membrane module (10). Figures 13.b and 13.c show the temperatures of the air outlet stream (14) as a function of the air stream inlet temperature (11). Figures 13.d and 13.e show the maximum temperatures inside the module as a function of the inlet temperature of the air stream (14). The results show that, for the cases considered in example 1, considering the total fixed membrane area, for the second membrane module (10) achieving complete oxidations of the residual current without reaching excessive temperatures that could degrade the module requires introducing excesses. high air flow and high inlet temperatures.

Figure 14 shows the results of example 1 where a practical case of the third membrane module (15) has been studied. Air has been considered as a stream rich in oxygen (14). The results show that, for the assumptions considered in Example 3, the pressure of the inlet air stream to the third membrane module and the imposed vacuum significantly improve oxygen extraction by reducing the membrane area necessary for the process.

Example 2

A second alternative of the procedure according to the invention is shown in figure 2.

This variant of the procedure presents an alternative in terms of the dosing of the oxygen-rich current in the modules M ¹ and M ² . In this case, the oxygen-rich stream (11) in the heat exchanger device (31) is introduced to the second membrane module (10). The current depleted in oxygen (14) from the second membrane module (10) is dosed by means of a system of dosing valves (44, 45 and 46) to recirculate this current to the first membrane module (6), to the third membrane module (15) and to the turbine (33). Thus, the stream of depleted oxygen (14) that comes from the second membrane module (10) is divided into three streams (41, 42 and 43) that are introduced into the dosing valves. The input stream to the first dosing valve (44) is a fraction of the lean air stream (41). The inlet stream to the second dosing valve (45) is a fraction of the depleted oxygen stream (42) with respect to (C 2 ) and the outlet stream is the oxygen-rich stream (48) of entrance to the third membrane module (15). The depleted oxygen stream (16) that comes from the third membrane module (15) and the outlet stream from the first dosing valve (44) are combined and introduced into a depleted stream into oxygen (40) which is introduced into the turbine (33). The input stream to the third dosing valve (46) is a fraction of the oxygen-depleted stream (43) that comes from the second membrane dome module (10). The output stream from the third dosing valve is the oxygen-rich stream (7) input to the first membrane module. This stream (7), as in the case of example 1, must contain an amount of oxygen less than the stoichiometric amount to completely oxidize the combustible stream (5), it is supplied to the third membrane module (15) as current (48) that supplies oxygen to the module (15) and to the turbine (33). In this way, the dosing of the dosing valves (44, 45, and 46) is carried out considering that the depleted oxygen outlet current (9) must be practically between pure N ² and the amount of oxygen that is to be produced (21).

Example 3

Figure 3 shows a particular example of a process according to the invention, an alternative process to produce O ² and CO ² . In this case, the first membrane module is omitted with respect to the first two examples (Figure 1 and Figure 2). It is observed that the fuel gas current (5) that comes out of the first heat exchanger (4) is the input current to the second membrane module (10). In this case All of the heated oxygen-rich stream (11) in the second heat exchanger system (31) is introduced to the second membrane module (10).

Example 4

Figure 4 shows a particular example - with possible variants, how it reads at the end of the paragraph - of a process according to the invention to produce N ² and CO ² . It can be seen that in this case the third membrane module is dispensed with with respect to the first two examples (Figure 1 and Figure 2). The oxygen-depleted outlet stream (14) from the second membrane module (10) is observed to be recirculated to the turbine (33) as the input stream. Additionally, depending on the final application of the gas streams obtained, the procedure can optionally incorporate a pressurization system for the different streams that are produced as shown in the figure. Therefore, a variant of this embodiment would be an embodiment in which the nitrogen and carbon dioxide streams obtained are not pressurized and therefore the compressors (49) and (51) would not be present.

In the event that the current is pressurized, for the CO ² pressurization system (49), the input current is the CO ² current (25) that comes from the separator condenser (24) and the output current is a CO ² stream (50) at the required service pressure. The nitrogen leaving the first membrane module (9) is cooled to practically room temperature by means of a heat exchanger (73), from which it leaves as a stream of N ² (74). Finally, there is a N ² pressurization system (51). The input stream to this pressurization system (51) is the N ² stream (74) that comes out of the heat exchanger (73). The output stream of the N ² pressurization system (51) is a stream of N ² (52) at the required service pressure. The dosing or control of the volumetric flow of the incoming and outgoing gas streams to the oxygen permeation membrane modules (6) M ¹ and M ² (10) is carried out by means of a system of valves (38 and 39) as in the case from example 1.

Example 5

Figure 5 shows a particular example of a process according to the invention for the production of N ² and O ² . In this case, the second membrane module is dispensed with with respect to the first two examples (Figure 1 and Figure 2). The partially oxidized combustible gaseous stream leaving the first membrane module (8) and the depleted oxygen-rich stream exiting the third membrane module (16) are introduced into a combustor (53) to finish oxidizing the combustible material of the current ga dare partially oxidized. The output stream from the combustor (54) is fed into the turbine (33).

The dosing or control of the volumetric flow of the incoming and outgoing gas streams to the oxygen permeation membrane modules M ¹ and M ² is carried out by means of a valve system u las (38 and 39) as in the case of example 1.

The nitrogen that comes out of the first membrane module (9) is cooled and pressurized in the same way and with the same components that are used in example 4, shown in figure 4.

Example 6

Figure ⁶ shows a particular example of a procedure according to the invention that includes two additional membrane modules (M ⁴ and M ⁵ ) (58) and (59) for the purification of the currents of N ² and CO ² . T he currents of N ² (9) and CO ² (13 ) produced in the first membrane module (6) and the second membrane module (10 ) respectively can contain quantities of significant amounts of oxygen considering the purity required in its subsequent applications. For the elimination of the oxygen that the streams to purify may contain, use will be made of oxygen permeation membrane modules where the stream to be purified enters the module as a stream that supplies oxygen to the system ((55) for N ² and (57) for CO ² ). As the figure shows, the gas or fuel current (55) enters these modules as a drag current for the additional modules. The input currents to the first additional module (56) are the combustible dry gas current (55) and the N ² current to be purified (9) that comes from the output of the first additional module. embrana (6). The output streams of the first additional membrane module (56) are the combustible dry gas stream (57) and the purified N ² stream (58). The input currents to the second additional module (59) are the combustible gaseous current (57) that comes from the output of the first additional membrane module (56) and the CO ² stream to be purified (13) that comes from the outlet of the second membrane module (10). The output currents of the second additional membrane module (59) are the combustible dry gas current (5) and the purified CO ² current (60). Finally, the oxygen extracted from the streams to be purified will cause a slight oxidation in the combustible gas stream that will cause a slight increase in temperature. The additional membrane modules (56 and 59) have a countercurrent flow distribution to ensure complete oxygen exchange from the streams to be purified to the combustible streams .

According to a further alternative, another way of purifying the CO ² and/or N ² streams can be the use of polymeric oxygen permeation membranes. In this case, the currents to be purified must be cooled down to atmospheric temperature and pressurized in order to carry out the process.

The completely oxidized combustible gas stream that comes from the second membrane module (13) is composed mainly of carbon dioxide and water vapor, as in the case of e Example 1. For its separation, the same components and procedure are used as in the case of Example 1.

The dosing or control of the volumetric flow of the incoming and outgoing gas streams to the oxygen permeation membrane modules M ¹ and M ² is carried out by means of a valve system u las (38 and 39) as in the case of example 1.

Example 7

Figure 7 shows a particular example of a procedure according to the invention that integrates the procedure described in example 1, shown in Figure 1, in a thermochemical revaluation process of biomase. In this case, the source of the fuel stream (C 1 ) is the biomass. The biomass is gasified by means of a thermochemical reactor (64). The input currents to the thermochemical reactor (64) are the biomass (61), a drag current (63), which is composed of an inert gas and may contain water vapor to improve the process (if necessary) and a current rich in oxygen (62) (unless the thermochemical process is a pyrolysis process, in which case no component is introduced that could cause oxidation of the m material). The output currents of the thermochemical reactor (64) is the gasified current (66) and the ashes that the biomass contains (65). The gasified stream is taken to a fractionation tower (67) to separate the light gases from the thickened gases. The input current to the fractionation tower (67) is the gasified current (66) that comes from the thermochemical reactor (64). The output currents are the light gas currents (68), each one of the product currents in which the fractionation is distributed (74, 75, 76, 77) and the liquid current of com heavy positions (78). In this case, the liquid stream of heavy compounds (78) represents the starting fuel stream for the membrane modules. Due to the fact that the current enters the process in the liquid phase, in this case the impulsion of the current is carried out with a hydraulic pump (79) at the operating pressure (considering the head losses of the different equipment downstream). The input stream to the hydraulic pump (79) is the heavy liquid stream (78) that comes from the fractionation tower (67). The output current of the hydraulic pump (79) is the liquid current of heavy or pressurized as (80). In this case for Bringing the fuel stream to the conditions of the membrane modules requires evaporation before heating the stream to operating temperature. An evaporator (81) is available for them to gasify the fuel stream. The input stream to the evaporator (12) is the liquid stream of heavy compounds (80) that comes from the hydraulic pump (79). The outlet current from the evaporator (12) is the gasified current of heavy compounds (3). A good design of the membrane modules can generate sufficient quantities of the CO ² and O ² streams to be considered for the feeding of the thermochemical reactor.

Example 8.

Membrane module for the production of N ² from air as an oxygen-rich stream and a combustible gaseous stream composed of CO and CO ² . The initial incoming fuel gas stream is composed of 57.1% CO in CO ² . The initial incoming fuel gas stream is diluted with CO 2 to slow down the temperature increase due to oxidation reactions such that r = - — Fco2------- - where is the initial fuel F

molar ratio between the input flow rate of CO ² diluent and the input flow rate of initial fuel gas and F is the molar flow rate of the input stream i. Different dilutions have been tested from er= 2.5 to r= 10. All streams enter at 700 °C. The air line is pressurized to 2.5 bar absolute pressure. Amounts of air at 2 5%, 50% and 75% of the stoichiometric amount of air have been used. The considered membrane module has 5 membranes of 380 cm 2 per membrane. The distribution of co-current and counter-current flows has been considered. The longitudinal distance between the entrance of the module's chambers and the exit of each chamber is 20 cm. The transport of oxygen through the membrane has been simulated from the following equation:

Where J ⁰² is the molar flux of oxygen per unit area, K is the permeability constant, paire is the total pressure in the air chamber, paradrag is the pressure in the drag chamber and xo ² ,is the molar fraction of oxygen in chamber i, T is the temperature, x is the longitudinal coordinate and tol is a parameter to avoid indeterminations in the calculation set to 10 -5. The K is calculated as a function of the temperature in order to be able to predict the improvement of the permeation as the temperature increases. The transmission of heat has been carried out considering the thermal conduction between the two walls of the membrane, through the equation:

gives

H a r _ kMEMB ^ ^ (Tsweep(x) - T air(x) )

where kMEMB is the thermal conductivity of the membrane, dA is the area differential of the membrane, dx is the length differential, Ti(x) is the temperature in the chamber i in the position x and x represents the longitudinal position. The oxidation reaction that occurs in the sweep chamber (69) is: CO 0 .5 02 ^ CO ² . The heat of reaction has been calculated using the enthalpy of reaction of the combustion reaction. The results are shown in Figure 11.

Example 9. Membrane module for the complete oxidation of a stream with combustible material from air as a stream rich in oxygen and a combustible gaseous stream composed of CO and CO ² . The gaseous fuel stream is composed of 9.5% CO in CO ² . The temperature of the inlet streams has been varied such that the air stream has been introduced at temperatures from 600 °C to 8 15 °C and the drag stream has been introduced at 600 °C and 700 °C. °C . The air line is pressurized to 2.5 bar absolute pressure. The air is introduced in excess, being A the molar relationship between the molar flow rate of inlet air (Faire) and the molar flow rate of stoichiometric air (Faire stoichiometric), such that A = - _F - _a - _i - _r - _e -- _e -- _s —

_tequio -- _m --

_he --

_tr - _i - _c - _o- . Different excesses of air have been tested, from A = 5 to A = 20. The considered membrane module has 5 membranes of 380 cm 2 per membrane. Distribution in co-current and countercurrent has been considered. The outlet temperatures of the air stream and the maximum temperature reached by the system have been measured. The longitudinal distance between the entrance of the module's chambers and the exit of each chamber is 20 cm. The transport of oxygen through the membrane has been simulated from the following equation:

Where J ⁰² is the molar flux of oxygen per unit area, K is the permeability constant, paire is the total pressure in the air chamber, paradrag is the pressure in the drag chamber and xO ² ,is the molar fraction of oxygen in chamber i, T is the temperature, x is the longitudinal coordinate and tol is a parameter to avoid indeterminations in the calculation set to 10 -5. The K is calculated as a function of the temperature in order to be able to predict the improvement of the permeation as the temperature increases. The transmission of heat has been carried out considering the thermal conduction between the two walls of the membrane, through the equation:

gives

C a |or = kMEMB ^ ^ (Tsweep(x) - T air(x) )

where kMEMB is the thermal conductivity of the membrane, dA is the area differential of the membrane, dx is the length differential, Ti(x) is the temperature in the chamber i in the position x and x represents the longitudinal position. The oxidation reaction that occurs in the sweep chamber (69) is: CO 0.5 02 ^ CO ² . The heat of reaction has been calculated using the enthalpy of reaction of the combustion reaction. The results are shown in figure 13.

Example 10. Membrane module for obtaining oxygen from air as a stream rich in oxygen and imposing a vacuum.

This example is intended to illustrate the third membrane module of examples 1, 2, 3, 5, 6 and 7. In these cases it is an O ² permeation from a current rich in O ² .

The inlet stream temperature has been varying from 900 °C to 1050 °C. Different air line pressurizations have been tested from 1 bar up to 5 bar absolute pressure. Two vacuum pressures have been tested: 50 m bar and 100 m bar. Different membrane areas have been studied (from 0.5 m3 to 10 m3). The equivalence between membrane area and number of membranes has been carried out considering 380 cm 2 membranes. Oxygen transport through the membrane has been simulated at starting from the following equation:

Where J ⁰² is the molar flux of oxygen per unit area, K is the permeability constant, paire is the total pressure in the air chamber, pvacuum is the pressure in the entrainment chamber, and xo ² ,is the mole fraction of oxygen in chamber i, T is the temperature, and x is the longitudinal coordinate. The K is calculated as a function of the temperature in order to be able to predict the improvement of the permeation as the temperature increases. The results are shown in Figure 14.

Example 11

Flat oxygen permeation membrane modules have been designed with various configurations shown in Figures 8, 9 and 10. These figures are not intended to give a complete sample of geom etries and fixed planes for the membrane modules, but to elucidate the internal distribution of the gas currents by the module. Likewise, there are more construction details that can be modified depending on the needs of the module. For example, the number of membranes in the module depending on the needs of the process area or the number of rails to conduct the currents to the chambers of the module or extract the gas from the chambers of the module (identified by the holes Figure 8.b, Figure 9.b and Figure 10.b) can be increased depending on the final dimensions of the module in order to guarantee a good distribution of the gas currents in each of the chambers.

Figure 8 shows the geometry of a flat membrane module (with 20 membranes) with a cross flow distribution. Figure 8.c shows the cross section B-B (Figure 8.b) of the membrane module with cross-flow distribution with the paths of the gas current that crosses the module in the B-B direction. Figure 8.d shows the cross section C-C (Figure 8.b) of the membrane module with cross-flow distribution with the paths of the gas current that crosses the module in the C-C direction (perpendicular to the B-B direction). Figures 8.c and 8.d show that the gas streams enter through the upper and lower part of the module and are extracted in the same way with the aim of minimizing pressure losses and equally distributing the inlet gas stream. by the different cameras of the module.

Figure 9 shows the geometry of a flat membrane module (with 20 membranes) valid for both a co-current distribution and a counter-current flow distribution. The cross sections A-A and B-B (Figure 9.b) are parallel planes, so that the gas currents shown in the figures obtained by means of these cut planes (9.c-h) circulate in the same trajectory with the same direction for the distribution of flows in co-current (Figures 9.c and 9.d) or with opposite directions for the distribution of flows in countercurrent (Figures 9.g and 9.h). Figures 9.c and 9.d illustrate the gas flow paths using the membrane module with a co-current flow configuration. Figure 9.e is an enlarged view of Figure 9.c to detail the flow distribution in the module. Figure 9.f is an enlarged view of Figure 9.d to detail the flow distribution in the module. Figures 9.g and 9.h illustrate the paths of the gas currents using the membrane module with a countercurrent flow configuration. Figures 9.c-h illustrate that the gas streams enter from the top and bottom of the module and are extracted in the same way with the aim of minimizing pressure losses and equitably distributing the inlet gas stream through the different chambers. of the module.

Figure 10 shows the geometry of a flat membrane module where the gas currents cross the membrane module several times in its longitudinal direction. This geometry allows for both a co-current distribution and a counter-current distribution of flows. Considering as "one step" each time the gas stream passes through the membrane in its longitudinal direction, Figure 10 represents a module with 3 passes per module with 6 membranes per pass. The cut planes AA and BB (Figure 10.b) are parallel planes, so that the gas currents shown in the figures obtained by means of these cut planes (10.ch) go on the same trajectory with the same direction for the distribution of flows in co-current (Figures.10.c and 10.d) or with opposite directions for the distribution of flows in countercurrent (Figures 10.g and 10.h). Figures 10.c and 10.d illustrate the gas flow paths using the membrane module with a co-current flow configuration. Figure 10.e is an enlarged view of Figure 10.c to detail the flow distribution in the module. Figure 10.f is an enlarged view of Figure 10.d to detail the flow distribution in the module. Figures 10.g and 10.h illustrate the paths of the gas currents using the membrane module with a countercurrent flow configuration. The gases enter the module from the inside for the distribution of flows in co-current (Figure 10.c and 10.d) and for Figure 10.g and the upper part for Figure 10.h. The gases leave the module through the upper part for the distribution of co-current flows (Figure 10.c and 10.d) and for Figure 10.g and the lower part for Figure 10.h.

Claims (42)

1. A process for generating and separating gases selectively characterized in that it comprises: - a first stage in which a gas phase fuel stream is passed, comprising combustible substances whose oxidation gives rise to gaseous products, and an oxygen-rich inlet stream through at least two oxygen separation membrane modules. oxygen, so that the two currents come into contact through the membranes and a heat exchange takes place between them, - a second stage of selective diffusion of oxygen from the oxygen-rich stream, towards the fuel stream, and such that the outlet streams of the membrane modules are, on the one hand, an oxygen-depleted or completely oxygen-free stream and, on the other hand, a partially oxidized or completely oxidized stream, - a third recovery stage of at least two separate outlet streams, of at least two gases selected from practically pure oxygen, nitrogen, carbon dioxide and hydrogen. 2. A process for selectively generating and separating gases, according to claim 1, characterized in that it comprises: - a first stage in which a gas phase fuel stream is passed, comprising combustible substances whose oxidation gives rise to gaseous products, and an oxygen-rich inlet stream through at least two oxygen separation membrane modules. oxygen, so that the two currents come into contact through the membranes and a heat exchange takes place between them, generating practically pure N2 in the first module, - a second stage of selective diffusion of oxygen from the oxygen-rich stream, towards the fuel stream, and such that the outlet streams of the membrane modules are, on the one hand, an oxygen-depleted or completely oxygen-free stream and, on the other hand, a partially oxidized or completely oxidized stream, - a third recovery stage of at least two separate outlet streams, of at least two gases selected from practically pure oxygen, nitrogen, carbon dioxide and hydrogen. A method according to claim 1, characterized in that the oxygen-rich input stream is selected from air, steam and combinations thereof. 4. A process according to any of claims 1 or 2, characterized in that in the second stage the oxidation of the fuel is complete. A process according to any one of the preceding claims, characterized in that the oxygen-rich input stream is air and the two separate output streams are nitrogen and carbon dioxide. A process according to any one of claims 1 to 3, characterized in that the oxygen-rich inlet stream is air and there are at least three separate outlet streams: oxygen, nitrogen and carbon dioxide. A process according to any one of claims 1 to 4, characterized in that the oxygen-rich input stream is steam and the two separate output streams are hydrogen and carbon dioxide. A process according to any one of claims 1 to 4, characterized in that the oxygen-rich stream is steam and there are at least three separate outlet streams: oxygen, hydrogen and carbon dioxide. 9. A method according to any one of the preceding claims, characterized in that the gas exchange between the two input currents to the membrane modules is carried out at a temperature between 600 °C and 1500 °C. 10. A method according to any one of the preceding claims, characterized in that it further comprises a stage of pressurizing the inlet streams in a first gas compressor device, at absolute pressures between 2 and 15 bar, obtaining pressurized inlet streams. A method according to any one of the preceding claims, characterized in that it further comprises a stage of preheating the pressurized inlet streams, with heat released by the outlet streams, obtaining preheated pressurized inlet streams. A process according to any one of the preceding claims, in which the flows of the combustible gas stream and the oxygen-rich stream are arranged in countercurrent. 13. A method according to any one of the preceding claims, in which the oxygen-depleted outlet stream is introduced into a turbine for its energy recovery. A method according to one of the preceding claims, in which the first gas compressor device and the turbine are connected to the same shaft. 15. A method according to one of the preceding claims, which is carried out in at least three modules selected from among: - a first membrane module in which the gasified fuel stream is partially oxidized, - a second membrane module in which the gasified fuel stream is completely oxidized, - a third membrane module in which oxygen extraction is carried out. A method according to claim 1, wherein cross-flow, co-current flow or counter-current flow is used in the second membrane module. 17. A process according to claim 15, in which CO2 and liquid water are produced from the oxidized combustible gaseous current that comes out of the second module, the water being condensed by means of a condenser-separator arranged at the outlet of the second module, from which two outlet streams: an oxidized combustible gas stream -composed mainly of CO2- and a stream of liquid water. A process according to one of the preceding claims, in which carbon dioxide and nitrogen are obtained, and a recirculation of part of the carbon dioxide or nitrogen obtained in the process is carried out, so that a dilution is produced. from the combustible gas stream and the heats of oxidation are absorbed A method according to claim 1, in which three membrane modules are used, and such that - all the oxygen-rich inlet stream coming from the second heat exchanger is fed into the second membrane module, - the oxygen-depleted stream exiting the second membrane module is metered by means of a valve system that partially circulates this stream: - to the first membrane module as a stream supplying oxygen as an oxygen-depleted stream containing an amount of oxygen less than the stoichiometric amount to fully oxidize the gasified fuel stream, and - to the third membrane module as a stream supplying oxygen to the third module and the turbine. 20. A method according to claim 1, wherein the second and third membrane modules are used, - all the gasified, fuel, pressurized heated input stream coming from the first heat exchanger is introduced into the second membrane module, and - all of the oxygen-rich input stream coming from the second heat exchanger is fed into the second membrane module. A method according to claim 1, wherein: - only the first and second membrane modules are used, - the oxygen-depleted outlet stream from the second membrane module is recirculated to the turbine as turbine inlet stream. 22. A method according to claim 21, in which a CO2 outlet stream and an oxygen-depleted stream are obtained from the modules where partial oxidation occurs and both outlet streams are pressurized after being cooled. A method according to claim 1, wherein the first and third membrane modules are used, - the partially oxidized fuel gas stream leaving the first membrane module and the oxygen-depleted output stream from the third membrane module are introduced into a combustor to finish oxidizing the partially oxidized fuel material of the gas stream, and - the output current of the combustor is introduced into the turbine. 24. A process according to claim 1, wherein additional membrane modules are used, in addition to the first, second and third membrane modules, in the additional modules the streams of gases produced in the first membrane module and the second membrane module removing oxygen from them, and - the combustible gas stream enters the additional modules as an entrainment stream. 25. A process according to the preceding claim in which the membrane modules have a countercurrent flow distribution to ensure complete oxygen exchange from the streams to be purified to the combustible streams. A process according to claim 24 in which the off-gas streams are purified by polymeric oxygen permeation membranes, after being cooled to room temperature and pressurized. 27. A process according to claim 1, in which the source of the combustible gasified stream is biomass, which is gasified by a thermochemical reactor, the input streams to the thermochemical reactor being: - biomass - a drag stream made up of an inert gas and, optionally, steam, - and, optionally, an inlet stream rich in oxygen. 28. A process, according to claim 1, in which the input stream, which contains combustible materials, comprises one or more products selected from among CO, H2, H2S, methane, liquefied petroleum gases, alcohols, olefins, peroxides, aromatic compounds, organic acids, organic amines, naphthas, asphalts, bitumen, gas oil, vegetable, animal or mineral oils or fats, coals, and mixtures thereof. 29. A process according to one of claims 1 to 13, in which two or more gaseous outlet streams have a purity greater than 95%, on a dry basis, of one of the following gases chosen from N2, O2, H2 and CO2. 30. An installation to carry out the procedure defined in one of the preceding claims, comprising at least: - two oxygen separation membrane modules - gas compressors that drive the input currents to the membrane modules - heat exchanger devices between incoming or outgoing gas streams in membrane modules, - a turbine arranged to receive at least gas from one of the membrane modules and produce work - at least two separate individual flue gas stream lines from the oxygen separation membrane modules and wherein each oxygen separation membrane module comprises an array of planar parallel membranes. 31. An installation according to claim 30, which additionally includes at least one membrane module based on ceramic ionic and electronic conductors, and made up of parallel and flat channels that facilitate contact between gaseous currents isolated by the membrane and whose single inlet a stream rich in oxygen, and as outputs (i) a reject stream, depleted in oxygen compared to the inlet stream, and (ii) a stream rich in oxygen with purity greater than 95% and which is under vacuum .between 1 and 750 mbar-. An installation according to claim 30, wherein the membrane modules comprise separation membranes based on ceramic ionic and electronic conductors, and porous ceramic supports. An installation according to claim 30, in which the membrane modules comprise a catalyst for the effective oxidation of the fuel components with oxygen diffusing through the membrane. An installation according to claim 30, in which the flow of the two currents, which facilitates the exchange of matter and heat, in the membrane modules is carried out in countercurrent and sufficient length is provided for an effective exchange. 35. An installation according to claim 30, which additionally includes at least one separation module based on porous polymeric or inorganic membranes selective for nitrogen diffusion and which allows obtaining a current enriched in nitrogen at temperatures below 400°C. from a pressurized air supply. An installation according to claim 30, further comprising a water and gas separation unit. 37. An installation according to claim 30 comprising at least: - a first oxygen separation membrane module, which has two inlets for - a first gasified stream of fuel and - an inlet stream rich in oxygen. - a first gas compressor that makes it possible to pressurize the combustible gas stream, and which leaves the compressor as a pressurized combustible gas stream, towards - a first heat exchanger device that allows the pressurized combustible gas stream to be heated and which leaves the exchanger as a stream preheated pressurized fuel gas - a second gas compressor that makes it possible to pressurize the oxygen-rich inlet stream, and which leaves the compressor as a pressurized oxygen-rich inlet stream - a countercurrent gas heat exchanger device that allows heating: - the oxygen-rich inlet stream pressurized to the inlet temperature to the first membrane module, and exiting the heat exchanger as a heated pressurized oxygen-rich inlet stream, - and an oxygen-depleted stream coming from a turbine - at least two separate individual gas outlet stream lines from second and third oxygen separation membrane modules and wherein each oxygen separation membrane module comprises an array of planar parallel membranes. An installation according to claim 30, in which at least one compressor and a turbine are axially coupled to use the mechanical energy of the expansion in the compression of a gas stream. 39. An installation according to claim 30, in which the coupling is carried out by means of axial turbine-compressors or turbocharger-type systems. 40. An installation according to claim 30, comprising three membrane modules and in which the outlet stream from the second membrane module is separated into three stream lines, each of which comprises a dosing valve, and of which which two of the current lines lead to the first or second module allowing the recirculation of gases, and the third current line leads to the third membrane module, allowing the progress of the process. An installation according to claim 30, comprising two membrane modules. An installation according to claim 30, comprising more than three membrane modules.